U.S. patent application number 12/741546 was filed with the patent office on 2011-04-28 for steric stabilized latex particulates.
Invention is credited to Sivapackia Ganapathiappan.
Application Number | 20110097497 12/741546 |
Document ID | / |
Family ID | 40678866 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110097497 |
Kind Code |
A1 |
Ganapathiappan; Sivapackia |
April 28, 2011 |
STERIC STABILIZED LATEX PARTICULATES
Abstract
The present invention is drawn to steric stabilized latex
particulates, methods of forming such particulates, inks containing
such particulates, and methods of ink-jetting inks containing such
particulates. A steric stabilized latex particulate for use in an
ink-jet ink can comprise a random copolymer of a steric
stabilization oligomer and a hydrophobic monomer.
Inventors: |
Ganapathiappan; Sivapackia;
(Los Altos, CA) |
Family ID: |
40678866 |
Appl. No.: |
12/741546 |
Filed: |
November 30, 2007 |
PCT Filed: |
November 30, 2007 |
PCT NO: |
PCT/US2007/024707 |
371 Date: |
May 5, 2010 |
Current U.S.
Class: |
427/256 ;
524/599; 528/271 |
Current CPC
Class: |
C08F 220/00 20130101;
C08F 2/22 20130101; C09D 11/30 20130101 |
Class at
Publication: |
427/256 ;
528/271; 524/599 |
International
Class: |
C09D 11/10 20060101
C09D011/10; C08G 63/12 20060101 C08G063/12; B05D 5/00 20060101
B05D005/00 |
Claims
1. A steric stabilized latex particulate for use in an ink-jet ink,
comprising a random copolymer of a steric stabilization oligomer
and a hydrophobic monomer.
2. The steric stabilized latex particulate of claim 1, wherein the
steric stabilization oligomer is selected from the group consisting
of: polymethylene oxide, substituted polymethylene oxide,
polyethylene oxide, substituted polyethylene oxide, polypropylene
oxide, substituted polypropylene oxide, acrylates thereof, and
combinations thereof.
3. The steric stabilized latex particulate of claim 2, wherein the
steric stabilization oligomer comprises methoxy ethanol; methoxy
ethoxy ethanol; methoxy polyethylene glycol; polyethylene glycol;
1-methoxy-2-propanol; 3-methoxy-1,2-propanediol; poly(ethylene
glycol-co-propylene glycol); polyethylene glycol with end groups of
amino, acid, alkyl, or acrylate including further substitutions
thereof; ethylene glycol monomethacrylate with ethylene oxide units
from 1 to 100; and combinations thereof.
4. The steric stabilized latex particulate of claim 1, wherein the
hydrophobic monomer is selected from the group consisting of:
styrene, p-methyl styrene, methyl methacrylate, hexyl acrylate,
hexyl methacrylate, butyl acrylate, butyl methacrylate, ethyl
acrylate, hydroxyethyl acrylate, ethyl methacrylate, hydroxyethyl
methacrylate, propyl acrylate, hydroxypropyl acrylate, propyl
methacrylate, hydroxypropyl methacrylate, vinylbenzyl chloride,
ethylhexyl acrylate, ethylhexyl methacrylate, isobutyl acrylate,
isobutyl methacrylate, cyclohexyl methacrylate, stearyl
methacrylate, alpha-methylstyrene, vinyl acetate, vinyl benzoate,
vinyl ethers such as vinyl methyl ether, vinyl phenyl ether, vinyl
butyl ether, allyl ether, maleimide derivatives such as N-phenyl
maleimide and N-methyl maleimide, and combinations thereof.
5. The steric stabilized latex particulate of claim 1, wherein the
hydrophobic monomer is at least one of styrene, methyl
methacrylate, butyl acrylate, butyl methacrylate, or hexyl
methacrylate.
6. The steric stabilized latex particulate of claim 1, wherein the
random copolymer further includes a second hydrophobic monomer
copolymerized therewith, said second hydrophobic monomer selected
from the group consisting of: styrene, p-methyl styrene, methyl
methacrylate, hexyl acrylate, hexyl methacrylate, butyl acrylate,
butyl methacrylate, ethyl acrylate, hydroxyethyl acrylate, ethyl
methacrylate, hydroxyethyl methacrylate, propyl acrylate,
hydroxypropyl acrylate, propyl methacrylate, hydroxypropyl
methacrylate, vinylbenzyl chloride, ethylhexyl acrylate, ethylhexyl
methacrylate, isobutyl acrylate, isobutyl methacrylate, cyclohexyl
methacrylate, stearyl methacrylate, alpha-methylstyrene, vinyl
acetate, vinyl benzoate, vinyl ethers such as vinyl methyl ether,
vinyl phenyl ether, vinyl butyl ether, allyl ether, maleimide
derivatives such as N-phenyl maleimide and N-methyl maleimide, and
combinations thereof.
7. The steric stabilized latex particulate of claim 6, wherein the
second hydrophobic monomer is at least one of styrene, methyl
methacrylate, butyl acrylate, butyl methacrylate, or hexyl
methacrylate.
8. The steric stabilized latex particulate of claim 1, wherein the
random copolymer further includes a hydrophilic monomer or
hydrophilic oligomer copolymerized therewith.
9. The steric stabilized latex particulate of claim 8, wherein the
hydrophilic monomer or hydrophilic oligomer is selected from the
group consisting of: ethylene oxide; propylene oxide; methylene
oxide; methoxy ethanol; methoxy ethoxy ethanol; methoxy
polyethylene glycol; polyethylene glycols; 1-methoxy-2-propanol;
3-methoxy-1,2-propanediol; poly(ethylene glycol-co-propylene
glycol); polyethylene glycol with end groups of amino, acid, alkyl,
or acrylate including further substitutions thereof; ethylene
glycol monomethacrylate with ethylene oxide units from 1 to 100;
and combinations thereof.
10. The steric stabilized latex particulate of claim 1, wherein the
steric stabilization oligomer has from about 2 to 1000 monomer
units.
11. The steric stabilized latex particulate of claim 1, wherein the
steric stabilization oligomer has from about 2 to 100 monomer
units.
12. The steric stabilized latex particulate of claim 1, wherein the
steric stabilization oligomer has from about 10 to 50 monomer
units.
13. A method of forming a steric stabilized latex particulate for
use in an ink-jet ink, comprising: a) reacting a cerium initiator
with a steric stabilized oligomer to form reactive steric
stabilization oligomers, and b) polymerizing a hydrophobic monomer
and the reactive steric stabilization oligomers in water to form
the steric stabilized latex particulate.
14. The method of claim 13, wherein the steric stabilized latex
particulate further comprises a surfactant.
15. The method of claim 13, wherein the step of polymerizing is by
emulsion polymerization.
16. The method of claim 13, wherein the cerium initiator is
selected from the group consisting of ammonium cerium (IV) nitrate,
ammonium cerium (IV) sulfate, and combinations thereof.
17. The method of claim 13, wherein the hydrophobic monomer is
selected from the group consisting of: styrene, p-methyl styrene,
methyl methacrylate, hexyl acrylate, hexyl methacrylate, butyl
acrylate, butyl methacrylate, ethyl acrylate, hydroxyethyl
acrylate, ethyl methacrylate, hydroxyethyl methacrylate, propyl
acrylate, hydroxypropyl acrylate, propyl methacrylate,
hydroxypropyl methacrylate, vinylbenzyl chloride, ethylhexyl
acrylate, ethylhexyl methacrylate, isobutyl acrylate, isobutyl
methacrylate, cyclohexyl methacrylate, stearyl methacrylate,
alpha-methylstyrene, vinyl acetate, vinyl benzoate, vinyl ethers
such as vinyl methyl ether, vinyl phenyl ether, vinyl butyl ether,
allyl ether, maleimide derivatives such as N-phenyl maleimide and
N-methyl maleimide, and combinations thereof.
18. The method of claim 17, wherein the hydrophobic monomer is
selected from the group styrene, methyl methacrylate, butyl
acrylate, butyl methacrylate, and hexyl methacrylate.
19. The method of claim 13, wherein the cerium initiator initiates
a free radical polymerization by forming a radical on a
stabilization group of the steric stabilized oligomer forming
reactive steric stabilization oligomers.
20. The method of claim 13, wherein the steric stabilization
oligomer is selected from the group consisting of: polymethylene
oxide, substituted polymethylene oxide, polyethylene oxide,
substituted polyethylene oxide, polypropylene oxide, substituted
polypropylene oxide, acrylates thereof, and combinations
thereof.
21. The method of claim 13, further comprising the step of
cross-linking the steric stabilized latex particulate.
22. The method of claim 13, wherein the step of polymerizing
further comprises copolymerizing a second hydrophobic monomer
therewith, said second hydrophobic monomer selected from the group
consisting of: styrene, p-methyl styrene, methyl methacrylate,
hexyl acrylate, hexyl methacrylate, butyl acrylate, butyl
methacrylate, ethyl acrylate, hydroxyethyl acrylate, ethyl
methacrylate, hydroxyethyl methacrylate, propyl acrylate,
hydroxypropyl acrylate, propyl methacrylate, hydroxypropyl
methacrylate, vinylbenzyl chloride, ethylhexyl acrylate, ethylhexyl
methacrylate, isobutyl acrylate, isobutyl methacrylate, cyclohexyl
methacrylate, stearyl methacrylate, alpha-methylstyrene, vinyl
acetate, vinyl benzoate, vinyl ethers such as vinyl methyl ether,
vinyl phenyl ether, vinyl butyl ether, allyl ether, maleimide
derivatives such as N-phenyl maleimide and N-methyl maleimide, and
combinations thereof.
23. The method of claim 13, wherein the step of polymerizing
further comprises copolymerizing a hydrophilic monomer or
hydrophilic oligomer therewith, said hydrophilic monomer or
hydrophilic oligomer selected from the group consisting of:
ethylene oxide; propylene oxide; methylene oxide; methoxy ethanol;
methoxy ethoxy ethanol; methoxy polyethylene glycol of molecular
weight 350, 550, 750, 1000, 2000 and 5000; polyethylene glycols of
molecular weight from 100 to 10,000; 1-methoxy-2-propanol;
3-methoxy-1,2-propanediol; polyethylene glycol-co-propylene glycol)
of molecular weight 100 to 5000; polyethylene glycol of molecular
weight from 100 to 5,000 with end groups of amino, acid, alkyl, and
acrylate including further substitutions thereof; ethylene glycol
monomethacrylate with ethylene oxide units from 1 to 100; and
combinations thereof.
24. An ink-jet ink, comprising: a) a vehicle, b) a colorant, and c)
the steric stabilized latex particulate of claim 1.
25. A method of ink-jet printing, comprising ink-jetting the
ink-jet ink of claim 24.
Description
BACKGROUND
[0001] There are several reasons that ink-jet printing has become a
popular way of recording images on various media Surfaces,
particularly paper and photo media substrates. Some of these
reasons include low printer noise, capability of high-speed
recording, and capability of multi-color recording. Additionally,
these advantages can be obtained at a relatively low price to
consumers. With respect to ink-jet ink chemistry, the majority of
commercial ink-jet inks are water-based. Thus, their constituents
are generally water-soluble, as in the case with many dyes, or
water dispersible, as in the case with pigments. Furthermore,
ink-jet inks often have low viscosity to accommodate high frequency
jetting and firing chamber refill processes common to ink-jet
architecture.
[0002] Attempts to improve ink characteristics such as durability,
fade-resistance, shelf-life, drop placement, resolution, viscosity,
etc., have included the addition of additives to the ink such as
biocides, buffers, latexes, dispersants, inorganic pigments,
chelating agents, etc. Continuing in this, it would be desirable to
provide methods, inks, and systems that provide improved ink
performance.
DETAILED DESCRIPTION
[0003] Before the present invention is disclosed and described, it
is to be understood that this invention is not limited to the
particular process steps and materials disclosed herein because
such process steps and materials may vary somewhat. It is also to
be understood that the terminology used herein is used for the
purpose of describing particular embodiments only. The terms are
not intended to be limiting because the scope of the present
invention is intended to be limited only by the appended claims and
equivalents thereof.
[0004] It must be noted that, as used in this specification and the
appended claims, the singular forms "a," "an," and "the" include
plural referents unless the context clearly dictates otherwise.
[0005] As used herein, "liquid vehicle" or "liquid medium" refers
to the fluid in which the steric stabilized latex particulates of
the present invention can be dispersed to form a latex suspension.
Often, the latex suspension can further include a colorant that can
be used as an ink-jet ink. Many liquid vehicles and vehicle
components are known in the art. Typical liquid vehicles can
include a mixture of a variety of different agents, such as
surfactants, co-solvents, buffers, biocides, sequestering agents,
viscosity modifiers, water, etc. Additionally, the terms "aqueous
liquid vehicle" or "aqueous vehicle" refer to liquid vehicles that
contain water as a major solvent. Such vehicles may also contain
additional organic co-solvents as is known in the art.
[0006] As used herein, "colorant" can include dyes and/or
pigments.
[0007] As used herein, "pigment" generally includes pigment
colorants, magnetic particles, aluminas, silicas, and/or other
ceramics or organo-metallics, whether or not such particulates
impart color. Pigments can be dispersed in a liquid vehicle with a
separate dispersing agent, or can have dispersing agent attached to
its surface, e.g., small molecule or polymeric dispersing agents.
Such pigments are well-known in the art.
[0008] As used herein, "dye" refers to compounds or molecules that
impart color to a vehicle or compound incorporating the dye. As
such, dye includes molecules and compounds that absorb
electromagnetic radiation or certain wavelengths thereof. For
example, dyes include those that fluoresce or those that absorb
certain wavelengths of visible light. Generally, dyes are water
soluble. Such dyes are well-known in the art.
[0009] As used herein, "steric stabilized oligomer," "steric
stabilization oligomer," "stabilized oligomer," "stabilization
oligomer," or the like, refers to an oligomer having a
stabilization group incorporate therein. Such oligomers are
generally reacted with a cerium initiator to form reactive
stabilization oligomers that can be subsequently incorporated into
steric stabilized latex particulates. Stabilization oligomers have
at least 2 polymerized monomeric units having a stabilization group
and may also contain other hydrophilic and hydrophobic monomers.
Generally, such stabilization oligomers are hydrophilic.
[0010] As used herein, "stabilization group" refers to hydrophilic
groups capable of stabilizing a polymer or oligomer in water
without the use of an ionic charge. Such stabilization groups
include polyethylene oxide, polypropylene oxide, polymethylene
oxide, poly(ethylene oxide-co-methylene oxide), substitutions
thereof and derivatives thereof. Such stabilization groups can be
incorporated into the steric stabilized latex particulates,
described herein, through the polymerization of reactive
stabilization oligomers.
[0011] As used herein, the term "about" is used to provide
flexibility to a numerical range endpoint by providing that a given
value may be "a little above" or "a little below" the endpoint. The
degree of flexibility of this term can be dictated by the
particular variable and would be within the knowledge of those
skilled in the art to determine based on experience and the
associated description herein.
[0012] As used herein, a plurality of items, structural elements,
compositional elements, and/or materials may be presented in a
common list for convenience. However, these lists should be
construed as though each member of the list is individually
identified as a separate and unique member. Thus, no individual
member of such list should be construed as a de facto equivalent of
any other member of the same list solely based on their
presentation in a common group without indications to the
contrary.
[0013] Concentrations, amounts, and other numerical data may be
expressed or presented herein in a range format. It is to be
understood that such a range format is used merely for convenience
and brevity and thus should be interpreted flexibly to include not
only the numerical values explicitly recited as the limits of the
range, but also to include all the individual numerical values or
sub-ranges encompassed within that range as if each numerical value
and sub-range is explicitly recited. As an illustration, a
numerical range of "about 1 wt % to about 5 wt %" should be
interpreted to include not only the explicitly recited values of
about 1 wt % to about 5 wt %, but also include individual values
and sub-ranges within the indicated range. Thus, included in this
numerical range are individual values such as 2, 3.5, and 4 and
sub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This same
principle applies to ranges reciting only one numerical value.
Furthermore, such an interpretation should apply regardless of the
breadth of the range or the characteristics being described.
[0014] It has been recognized that it would be advantageous to
develop steric stabilized latex particulates suitable for
development over a wide variety of applications. In accordance with
this, the present invention is drawn to compositions and methods
having a steric stabilized latex particulate for use in an ink-jet
ink. It is noted that when discussing a steric stabilized latex
particulate or a method of formulating such a latex particulate,
each of these discussions can be considered applicable to each of
these embodiments, whether or not they are explicitly discussed in
the context of that embodiment. Thus, for example, in discussing
the steric stabilization oligomer present in the steric stabilized
latex particulate, those steric stabilization oligomers can also be
used in a method for making such steric stabilized latex
particulates, and vice versa.
[0015] As such, with these definitions in mind, a steric stabilized
latex particulate, in accordance with embodiments of the present
invention, can comprise a random copolymer of a steric
stabilization oligomer and a hydrophobic monomer. For example, in
one embodiment, an oligomer chain (not merely its individual
monomers) can be randomly copolymerized with a hydrophobic
monomer.
[0016] In another embodiment, a method of forming a steric
stabilized latex particulate for use in an ink-jet ink can comprise
the steps of reacting a cerium initiator with a steric stabilized
oligomer to form reactive steric stabilization oligomers, and
polymerizing a hydrophobic monomer and the reactive steric
stabilization oligomers in water to form the steric stabilized
latex particulate. Additionally, an ink-jet ink can comprise a
vehicle, a colorant, and a steric stabilized latex particulate as
described herein. In one embodiment, a method of ink-jet printing
can comprise ink-jetting an ink-jet ink as described herein.
[0017] The formation of a steric stabilized latex particulate in
accordance with the above embodiments provides several advantages.
For example, steric stabilized latex particulates can increase the
film stability of the ink while maintaining the T.sub.g of the
polymer. The present steric stabilized latex particulates can also
improve the durability of the ink and resulting prints when
ink-jetted. Additionally, these steric stabilized latex
particulates can allow more flexible ink formulation since they do
not necessarily require specific pH ranges and do not necessarily
affect the resulting ionic strength of the vehicle or ink.
[0018] The latex particulates of the present invention can be
prepared through conventional free radical addition of a monomer
mixture through emulsion polymerization. As previously discussed,
the steric stabilized latex particulates described herein include
steric stabilized oligomers, hydrophobic monomers, and/or
hydrophilic monomers. Steric stabilized oligomers generally include
at least two monomers having steric stabilization groups. However,
the oligomers may also include other hydrophilic and hydrophobic
monomers. As such, when discussing hydrophobic and hydrophilic
monomers, such a discussion can refer to those used in the
polymerization with the steric stabilization oligomers or those
monomers that have been incorporated into such oligomers. However,
it is noted that an oligomer chain is what is ultimately
copolymerized with other hydrophobic monomers. For example, a
steric stabilized oligomer may contain at least two units of
ethylene oxide and one monomer unit of methacrylate. Such an
oligomer can be polymerized with methacrylate and styrene to form a
steric stabilized latex particulate. As such, it is recognized that
the methacrylate can be properly referred to as a hydrophobic
monomer that is part of the steric stabilized oligomer and a
hydrophobic monomer that is polymerized with the oligomer to form a
steric stabilized latex particulate. Therefore, hydrophobic and
hydrophilic monomers, as described herein, can be used in the
steric stabilized oligomers and/or the steric stabilized latex
particulates described herein.
[0019] In one embodiment, the steric stabilization oligomer can be
selected from the group consisting of: polymethylene oxide,
substituted polymethylene oxide, polyethylene oxide, substituted
polyethylene oxide, polypropylene oxide, substituted polypropylene
oxide, acrylates thereof, and combinations thereof. In another
embodiment, the steric stabilization oligomer can be selected from
the group consisting of: methoxy ethanol; methoxy ethoxy ethanol;
methoxy polyethylene glycol (e.g., molecular weight 350, 550, 750,
1000, 2000 or 5000); polyethylene glycol (e.g., molecular weight
from 100 to 10000); 1-methoxy-2-propanol;
3-methoxy-1,2-propanediol; poly(ethylene glycol-co-propylene
glycol) (e.g., molecular weight 100 to 5000); polyethylene glycol
(e.g., molecular weight from 100 to 5000 with end groups of amino,
acid, alkyl, and acrylate including further substitutions thereof);
ethylene glycol monomethacrylate (e.g., with ethylene oxide units
from 1 to 100); and combinations thereof. Additionally, the steric
stabilization oligomer can contain hydrophobic monomers.
[0020] Suitable hydrophobic monomers include styrene, p-methyl
styrene, methyl methacrylate, hexyl acrylate, hexyl methacrylate,
butyl acrylate, butyl methacrylate, ethyl acrylate, hydroxyethyl
acrylate, ethyl methacrylate, hydroxyethyl methacrylate, propyl
acrylate, hydroxypropyl acrylate, propyl methacrylate,
hydroxypropyl methacrylate, vinylbenzyl chloride, ethylhexyl
acrylate, ethylhexyl methacrylate, isobutyl acrylate, isobutyl
methacrylate, cyclohexyl methacrylate, stearyl methacrylate,
alpha-methylstyrene, vinyl acetate, vinyl benzoate, and, vinyl
ethers such as vinyl methyl ether, vinyl phenyl ether, vinyl butyl
ether, allyl ether, maleimide derivatives such as N-phenyl
maleimide and N-methyl maleimide, and combinations thereof.
[0021] In one embodiment, the steric stabilized latex particulates
can be polymerized from a reactive steric stabilized oligomer and a
hydrophobic monomer. In another embodiment, the steric stabilized
latex particulates can be polymerized from a reactive steric
stabilized oligomer, a first hydrophobic monomer, and a second
hydrophobic monomer. In yet another embodiment, the steric
stabilized latex particulates can be polymerized from a reactive
steric stabilized oligomer, a first hydrophobic monomer, a second
hydrophobic monomer, and a hydrophilic monomer. Such first and
second hydrophobic monomers can be the same or different.
Additionally, a third hydrophobic monomer can be further included
in the polymerizations described herein.
[0022] Hydrophilic monomers described herein can include ethylene
oxide, propylene oxide, methylene oxide, substitutions thereof, and
combinations thereof. Additionally, hydrophilic monomers can
include oligomers such as, methoxy ethanol; methoxy ethoxy ethanol;
methoxy polyethylene glycol (e.g., molecular weight 350, 550, 750,
1000, 2000 or 5000); polyethylene glycols (e.g., molecular weight
from 100 to 10000); 1-methoxy-2-propanol;
3-methoxy-1,2-propanediol; poly(ethylene glycol-co-propylene
glycol) (e.g., molecular weight 100 to 5000); polyethylene glycol
(e.g., molecular weight from 100 to 5,000 with end groups of amino,
acid, alkyl, and acrylate including further substitutions thereof);
ethylene glycol monomethacrylate (e.g., with ethylene oxide units
from 1 to 100); and combinations thereof.
[0023] As previously discussed, the steric stabilization oligomers
have at least two monomers having a stabilization group(s). In one
embodiment, the steric stabilization oligomer has from about 2 to
1000 polymerized monomer units. In another embodiment, the steric
stabilization oligomer has from about 2 to 100 polymerized monomer
units. In still another embodiment, the steric stabilization
oligomer has from about 10 to 50 polymerized monomer units.
[0024] The methods and compositions described herein generally use
a cerium compound as a free radical initiator for subsequent
polymerization of a monomer/oligomer emulsion mixture to form the
steric stabilized latex particulates. The cerium initiator can be
any compound containing cerium that is capable of forming a radical
on a steric stabilization group containing oligomer. In one
embodiment, the cerium initiator can be a member selected from the
group consisting of ammonium cerium (IV) nitrate, ammonium cerium
(IV) sulfate and combinations thereof. In another embodiment, the
cerium initiator can be ammonium cerium (IV) nitrate. Generally,
the cerium initiator can initiate a free radical polymerization by
forming a radical on a stabilization group of the steric stabilized
oligomer thereby forming a reactive steric stabilized oligomer.
Such a reactive stabilized oligomer can then initiate
polymerization with other hydrophobic and/or hydrophilic monomers
to form a steric stabilized latex particulate. As such, with the
use of cerium initiators, the polymerization can incorporate
hydrophobic monomers and hydrophilic monomers. In these compounds,
cerium can be replaced with other metals such as actinium,
lanthanum, yttrium, scandium, and thorium.
[0025] An aqueous emulsion of hydrophobic monomers, hydrophilic
monomers, and/or steric stabilization oligomers can be prepared
using emulsion polymerization synthesis. The thickness of the
steric stabilized latex particulates can be any suitable thickness,
but is typically greater than 50 nm to allow adequate film
formation to occur on a media substrate upon printing. Typically,
the selected steric stabilized latex particulate can be sized below
350 nm. In one embodiment, the steric stabilized latex particulate
diameter can be from about 100 to 300 nm, though diameters outside
of this range may be appropriate as well for certain
applications.
[0026] The latex can also be a dispersion stabilized through
incorporation of a monomer or monomers that promote latex surface
charge. For example, such charge forming monomers include acrylic
acid, methacrylic acid, vinyl benzoic acid, and
methacryloyloxyethylsuccinate. The charge forming monomers
typically comprise from 0.5 wt % to 20 wt %, preferably 3 wt % to
10 wt %, of the monomer mix by weight and are typically neutralized
after latex polymerization to form salts. Such salts may be formed
through the reaction of a monomer carboxylic acid with potassium
hydroxide or other similar salting agent. As such, incorporation of
acid moities can further improve stability to latex particles.
[0027] Particle dispersion stability is also influenced by particle
density, which influences the ability of particles to settle within
ink-jet architecture microchannels. In the present invention, the
monomer/oligomer mixture can be selected to collectively produce
latex particles having a density of 0.995-1.10 g/cm.sup.3,
preferably from about 1.03-1.05 g/cm.sup.3. In most instances, the
liquid vehicle of aqueous ink jet inks has a density on the order
of 1.01-1.02 g/cm.sup.3, though this is not required.
[0028] Other materials, such as surfactants, can generally also be
used to control the latex particle size during polymerization and
can also be selected to provide additional particle dispersion
stability. Such surfactants are often adhered to the particle
surface to minimize thermal stripping under thermal architecture
firing conditions.
[0029] Additionally, the surface dielectric constant of the steric
stabilized latex particulates of the present invention can be from
2.0 to 3.0, and can be below 2.8 in one embodiment. This property
can be useful to sufficiently anchor surfactants against thermal
shear stripping in thermal ink-jet architecture. Stabilization can
also be facilitated by the incorporation of 0.5 wt % to 5 wt %,
preferably 1 wt % to 2 wt %, of addition of a multimer, preferably
a dimer, capable of forming cross-links between polymer chains in
the latex particle. Such a multimer is represented by ethylene
glycol dimethacrylate, for example. As such, in one embodiment, the
steric stabilized latex particulate can be cross-linked. These
narrow ranges of cross-linking have been found beneficial to
maintain the integrity of the latex under the high thermal shear
conditions of thermal ink jetting while not adversely impacting its
room temperature film-forming properties. Such cross-linking is
helpful for latexes having glass transition temperatures below
50.degree. C. Room temperature film-forming latexes generally
require glass transition temperatures in the range of 0.degree. C.
to 50.degree. C., preferably 10.degree. C. to 40.degree. C. Higher
glass transition temperature ranges may be selected when latex
coagulation is accomplished at a higher than ambient temperature,
for example by heated fuser roller.
[0030] With these parameters in place regarding some of the
possible steric stabilized latex particulates that can be formed, a
discussion of dispersion fluids, e.g., inks, etc., is useful to
exemplify how these latex particulates can be implemented for use
in accordance with an embodiment of the present invention.
Typically, inks include a colorant dispersed in a liquid vehicle.
Typical liquid vehicle formulation that can be used with the
latexes described herein can include water, and optionally, one or
more co-solvents present in total at from 0.1 wt % to 50 wt %,
depending on the jetting architecture. Further, one or more
non-ionic, cationic, and/or anionic surfactant can be present,
ranging from 0.01 wt % to 5.0 wt %. The balance of the formulation
can be purified water, or other vehicle components known in the
art, such as biocides, viscosity modifiers, materials for pH
adjustment, sequestering agents, preservatives, and the like.
Typically, the liquid vehicle is predominantly water.
[0031] Classes of co-solvents that can be used can include
aliphatic alcohols, aromatic alcohols, diols, glycol ethers,
polyglycol ethers, caprolactams, formamides, acetamides, and long
chain alcohols. Examples of such compounds include primary
aliphatic alcohols, secondary aliphatic alcohols, 1,2-alcohols,
1,3-alcohols, 1,5-alcohols, ethylene glycol alkyl ethers, propylene
glycol alkyl ethers, higher homologs (C.sub.6-C.sub.12) of
polyethylene glycol alkyl ethers, N-alkyl caprolactams,
unsubstituted caprolactams, both substituted and unsubstituted
formamides, both substituted and unsubstituted acetamides, and the
like. Specific examples of solvents that can be used include
trimethylolpropane, 2-pyrrolidinone, and 1,5-pentanediol.
[0032] One or more of many surfactants can also be used as are
known by those skilled in the art of ink formulation and may be
alkyl polyethylene oxides, alkyl phenyl polyethylene oxides,
polyethylene oxide block copolymers, acetylenic polyethylene
oxides, polyethylene oxide (di)esters, polyethylene oxide amines,
protonated polyethylene oxide amines, protonated polyethylene oxide
amides, dimethicone copolyols, substituted amine oxides, and the
like. It is to be noted that the surfactant that is described as
being usable in the liquid vehicle is not the same as the
surfactant that is described as being adhered to the surface of the
latex particulate, though many of the same surfactants can be used
for either purpose.
[0033] Consistent with the formulation of this invention, various
other additives may be employed to optimize the properties of the
ink composition for specific applications. Examples of these
additives are those added to inhibit the growth of harmful
microorganisms. These additives may be biocides, fungicides, and
other microbial agents, which are routinely used in ink
formulations. Examples of suitable microbial agents include, but
are not limited to, Nuosept, Ucarcide, Vancide, Proxel, and
combinations thereof.
[0034] Sequestering agents, such as EDTA (ethylene diamine tetra
acetic acid), may be included to eliminate the deleterious effects
of heavy metal impurities, and buffer solutions may be used to
control the pH of the ink. From 0 wt % to 2.0 wt %, for example,
can be used. Viscosity modifiers and buffers may also be present,
as well as other additives known to those skilled in the art to
modify properties of the ink as desired. Such additives can be
present at from 0 wt % to 20.0 wt %.
[0035] In accordance with embodiments of the present invention, the
steric stabilized latex particulates of the present invention can
be present in an ink-jet ink at from about 0.5 wt % to about 15 wt
%. In one embodiment, the steric stabilized latex particulates of
the present invention can be present in an ink-jet ink at from
about 2 wt % to about 4 wt %.
EXAMPLES
[0036] The following examples illustrate embodiments of the
invention that are presently known. Thus, these examples should not
be considered as limitations of the present invention, but are
merely in place to teach how to make compositions of the present
invention. As such, a representative number of compositions and
their method of manufacture are disclosed herein.
Example 1
Preparation of a Steric Stabilized Latex Particulate
[0037] Methyl methacrylate (8 g), hexyl acrylate (8 g), and
polyethylene oxide (M.W. 2000, 4 g) are mixed and emulsified in
water (38 g) using the surfactant Rhodafac RS 710 (1.66 g of 30%
solution). Ammonium cerium (IV) nitrate (1 g) is added and heated
to 90.degree. C. for 4 hours. The cerium compound with oxidation
state of +4 is reduced to +2 while generating a radical on the
polyethylene oxide randomly. This radical further reacts with the
hydrophobic monomers (methyl methacrylate, hexyl acrylate)
resulting in a steric stabilized latex particulate incorporating
all three components, e.g., latex particulates including
polymerized methyl methacrylate, hexyl acrylate, and oligomers of
polyethylene oxide.
Example 2
Preparation of a Cross-Linked Steric Stabilized Latex
Particulate
[0038] Polyethylene oxide oligomer (2000 M.W., 4 g), butyl
acrylate, (8 g), styrene (8 g), and ethylene glycol dimethacrylate
(0.2 g) are mixed and emulsified in water (60 g) using a
surfactant. Ammonium cerium (IV) nitrate (1 g) is added and heated
to 90.degree. C. for 4 hours. The cerium compound with oxidation
state of +4 is reduced to +2 while generating a radical on the
polyethylene oxide substituent of the oligomer randomly. This
radical further reacts with the hydrophobic monomers (styrene,
butyl acrylate and ethylene glycol dimethacrylate) and hydrophilic
monomer (polyethylene oxide) resulting in a steric stabilized latex
particulate incorporating all four components. During the
polymerization, ethylene glycol dimethacrylate cross-links the
developing steric stabilized latex particulate, e.g., latex
particulates including polymerized butyl acrylate, styrene, and
oligomers of polyethylene oxide.
Example 3
Preparation of an Ink Containing a Steric Stabilized Latex
Particulate
[0039] An ink is prepared using the steric stabilized latex
particulates of Example 1 as outlined in Table 1:
TABLE-US-00001 TABLE 1 Component Wt % Latex of Example 1 or 2
0.1-10 Propylene glycol monobutyl ether 0.5-5 Ethoxylated glycerol
(LEG-1) 0.5-15 2-pyrrolidinone 0.5-15 2-ethyl-2-hydroxymethyl-1,3-
0.5-15 propanediol (EHPD) Surfactant 0.001-10 Pigment 0.1-10 Water
balance
[0040] While the invention has been described with reference to
certain preferred embodiments, those skilled in the art will
appreciate that various modifications, changes, omissions, and
substitutions can be made without departing from the spirit of the
invention. It is intended, therefore, that the invention be limited
only by the scope of the following claims.
* * * * *